1. Field of the Invention
The present invention relates to a golf club head.
2. Description of the Related Art
As the sizes of golf club heads typified by a wood golf club head increase each year, the influence of the air resistance upon a swing increases. As the air resistance increases, the head speed may lower, leading to a decrease in flight distance of a struck golf ball. Japanese Patent Laid-Open No. 2011-528263 proposes a golf club head manufactured using a technique of reducing the air resistance.
A golf club head preferably has a shape which allows the golfer to easily get ready for address. Therefore, when the air resistance is reduced by improving the head shape, a shape which makes the golfer experience too much incongruence is undesirable.
Also, during a swing, the orientation of the face portion with respect to the moving direction of the golf club head gradually changes, so the head moving direction comes close to the orientation of the face portion immediately before impact. To prevent a decrease in flight distance of a struck golf ball, it is effective to reduce the air resistance in the period from the last half of a down swing in which the golf club head accelerates until impact. In general, the face portion has a flat surface or slightly curved surface, and has a shape which is susceptible to the air resistance of an air current in a direction normal to this surface.